The invention relates to optical fibers and optical fiber preforms, especially optical fiber preforms incorporating powders with selected compositions to yield a fiber with desired properties. Furthermore, the invention relates to processes to form fiber preforms by incorporating particles with desired compositions within the fiber preform.
The demand for high bandwidth telecommunication channels has resulted in the dramatic growth in optical communication transmission. Generally, these optical communication systems are built upon optical fiber transmission. Optical fibers generally can be formed from a glass material with desirable optical properties.
Optical fibers are generally very thin. The fibers generally have a core with an index-of-refraction different from a cladding layer surrounding the core. In particular, generally a core has a higher index-of-refraction than the cladding such that the light of a selected wavelength undergoes total internal reflection at the boundary between the core and cladding to keep the light within the core. The difference in index-of-refraction can be introduced by selection of the composition of the core materials to be appropriately different from the composition of the cladding material. In addition, the composition of the optical materials can be selected to alter optical properties of the fiber, such as absorption and emission properties.
Optical fibers are generally pulled from a larger block of glass material. The block from which the fiber is puller is called a fiber preform. The fiber preform is heated to an appropriate temperature to pull a fiber at a suitable rate with a desired thickness. The composition of the preform determines the resulting composition of the resulting fiber.
In a first aspect, the invention pertains to an optical fiber preform comprising a glass preform structure with an inner cavity and a powder within the inner cavity. The powder has an average primary particle size less than about 1 micron.
In another aspect, the invention pertains to a method for forming an optical fiber preform. The method comprises pouring a slurry into a glass preform structure. The slurry comprises a dispersion of particles having an average primary particle size less than about 1 micron.
In a further aspect, the invention pertains to a method for forming an optical fiber preform in which the method comprises directing a product stream in a flowing reactor into a glass preform structure. At least a portion of the product stream is harvested within a cavity in the glass preform structure. In some embodiments, the flowing reactor comprises radiation beam intersecting a reactant stream at a reaction zone at which the product stream is generated.
In an additional aspect, the invention pertains to a method for forming an optical fiber preform in which the method comprises inserting an insert within a glass preform structure. The insert generally comprises a powder coating in which the powder coating comprises particles with an average primary particle diameter of no more than a micron. In some embodiments, the powder coating is formed in a flowing reactor by placing the insert in a product stream of the flowing reactor. In some embodiments, the flowing reactor comprises a radiation beam intersecting a reactant stream at a reaction zone at which the product stream is generated.